Written by Horav Yosef Yeshaya Braun, member of the Badatz of Crown Heights
The question of whether it’s permissible to carry a gun on Shabbos entails two issues: muktzah (objects which are “set aside” and may not be moved during Shabbos) and hotza’ah (carrying in the public domain) in a place where there is no eiruv.
The second issue is rather clear-cut: only clothing and personal ornaments are permitted to be carried on one’s person on Shabbos, and a gun is neither. The argument that a gun can serve as a fashion accessory is belied by the prophecy that all weapons will be crushed and turned into constructive tools, such as plowshares, when Moshiach comes, indicating that the Torah does not recognize any decorative value in weaponry.
A gun’s muktzah status, however, is subject to discussion among contemporary poskim; the question is whether it’s a kli she’melachto l’issur (a tool whose primary function is forbidden on Shabbos) since it was crafted for the purpose of killing, or whether it’s a kli she’melachto l’heter (a tool whose primary function is permitted on Shabbos) since its main objective is to instill fear. Carrying a concealed weapon seems to indicate that its use is primarily l’issur, while carrying it openly could suggest that it’s l’heter.
If there’s concern about a possible threat which would justify carrying a gun on Shabbos, even if it’s muktza or there’s no eiruv, a local rav with an understanding of the prevalent conditions must be consulted to determine whether the current threat is significant enough to justify carrying a gun on Shabbos.